Every so often, the photo you take through your car window works. Usually it doesn't. This is a simple arrangement, water on the glass in the foreground, tree shapes in the background. I like the texture of the water, and having focus on that plane seems to be effective. Focus on the background would likely reveal more detail than is needed, and create an overall softening effect from the rainy window. The roughly triangular arrangement of the branches, plus some elements at the bottom, provides flow for the eye to explore.
